The Walbro carb gets it's crankcase pulse through a hole in the carb mount attached to the cylinder. That is, unless the previous owner tapped the diaphragm cover and tapped the crankcase so that a different carb stand-off could be used.

Usually the Walbro carbs that have two connectors have a primer bulb and the connector on the carb body goes to the tank suction line with the outlet on the bottom of the prime bulb to a vent line.